There are several reasons that ink-jet printing has become a popular way of recording images on various media surfaces, particularly paper. Some of these reasons include low printer noise, capability of high-speed recording, and multi-color recording. Additionally, these advantages can be obtained at a relatively low price to consumers.
Though there has been great improvement in ink-jet printing, accompanying this improvement are increased demands by consumers in this area, e.g., higher speeds, higher resolution, full color image formation, increased stability, etc. As new ink-jet inks and print engines are developed, there have been several traditional characteristics to consider when evaluating the ink in conjunction with a printing surface or substrate. Such characteristics include edge acuity and optical density of the image on the surface, gloss, black to color bleed control, dry time of the ink on the substrate, adhesion to the substrate, lack of deviation in ink droplet placement, resistance of the ink after drying to water and other solvents, long term storage stability, and long term reliability without pen material degradation or nozzle clogging.
However, ink-jet prints have also been known for poor durability when exposed to water or high humidity. This results from the use of water-soluble and water dispersible colorants within the water-based ink. In response to this problem, latex polymers that are compatible with ink-jet inks have been incorporated with the inks. The latex can consist of small micron or submicron hydrophobic polymeric particles of high molecular weight that are dispersed in the aqueous ink-jet ink. When printed as part of an ink-jet ink, a latex component of the ink can form a film on a media surface, entrapping and protecting the colorant within the hydrophobic print film. While latexes can improve overall durability, they often hamper jettability and reliability. Accordingly, investigations continue into developing latex ink formulations that have acceptable durability while maintaining jettability and reliability.